WASHINGTON - The Interior Department said Friday it approved Shell Oil Co.'s plan to respond to potential oil spills in the Chukchi Sea, bringing the company closer to drilling off the northern coast of Alaska.

Shell hasn't yet received approval of its Beaufort Sea oil-spill response plan and must still get permits for each well it wants to drill. The Bureau of Safety and Environmental Enforcement said it also must inspect and approve various pieces of equipment Shell will use for the effort.

Royal Dutch Shell's Houston-based arm, which also has received approval for its Beaufort and Chukchi exploration plans, hailed the spill-response plan's approval as a major step toward starting to drill in July. Shell wants to drill six exploratory wells over the next two summers in the Chukchi Sea in shallow waters 70 miles off the coast. It must stop drilling 38 days before ice starts building up in the water, typically around Nov. 1.

Since 2005, Shell has spent over $4 billion on its goal to drill in the Beaufort and Chukchi seas. But litigation and appeals of various stages of Shell's application delayed its plans.

Environmental and Alaskan native groups have opposed the drilling. They say no proven technology exists to clean crude from the icy waters or to contain a spill.

Arctic expertise

Pete Slaiby, Alaska exploration manager for Shell, said in an email his company's drilling plans "will continually be guided by our extensive Arctic expertise, solid scientific understanding of the environment and world-class capabilities."

Revamped plan

Deputy Interior Secretary David Hayes said Shell had revamped its response plan so it could handle a spill five times bigger than under a previous proposal.

James Watson, director of the federal offshore safety bureau, said the plan builds on lessons from the Deepwater Horizon oil spill. He said Shell would have tougher preventative measures, such as stronger blowout preventers; systems to cap and contain a blowout; numerous vessels nearby; and an extra rig that could drill a relief well.

Some environmental groups remain critical.

"President Obama knows that if a major oil spill happened today in the Arctic, it would be impossible to clean it up due to environmental conditions like hurricane-force winds, 10-foot waves, cold temperatures and poor visibility," Earthjustice attorney Holly Harris said in a statement Friday.